The Book of Exogenesis: In the beginning was the word, and the word was a meteorite...
Earlier this month, a report, based on NASA studies of meteorites found on Earth, suggested that some building blocks of DNA may have been formed in space.
As it turns out, DNA components have been found on meteorites before, but it's never been entirely clear if the space rocks came to Earth bearing these molecules, or if they were contaminated upon arrival. Furthermore, this recent study of meteorites was the first to discover trace amounts of three molecules -- purine, 2,6-diaminopurine, and 6,8-diaminopurine -- which, as nucleobase analogues, provide us with the first piece of solid evidence that the compounds in the meteorites came from space and not terrestrial contamination.
This news, which propagated wildly through the blogosphere in its own form of directed panspermia, led me to bone up on its potential ramifications: what do DNA-saturated space rocks imply about the inherent properties of life? Do they support the theory of panspermia, or exogenesis?
The idea of panspermia has been around since the Greek philosopher Anaxagoras posited that the universe is made of an infinite number of spermata (seeds), coining the word "panspermia," or "all seeds," in the fifth century B.C. Shortly thereafter, Aristotle debunked Anaxagoras, putting forth a theory of spontaneous generation that held sway for over two thousand years. Since then, the idea has gone rogue, popping in and out of scientific and popular consciousness; it can be found in the writings of Berzelius, Kelvin, von Helmholtz and the Swedish scientist Svante Arrhenius in the early 1900s.
The British astronomer (and science-fiction writer) Sir Fred Hoyle, in cahoots with collaborator Chandra Wickramasinghe, argued that "terrestrial biology is not a closed system." He further maintained that not only is panspermia responsible for the origins of life on Earth, but that life-forms continue to enter the Earth's atmosphere in "genetic storms," and may be the key factors in the genetic novelty necessary for macroevolution. Hoyle was a scientific heretic -- rumor has it he was denied a Nobel prize because of his zeal for spaceborn primeval molecules -- and panspermia, as a theory, has always relied on hard-to-procure evidence of extraterrestrial life to have any real credibility. Both factor into panspermia's sticky dubiousness, and hence a concrete fragment of corroboration, like molecular compounds on meteorites, is a significant boon to this oft-maligned idea.
Of course, the "DNA meteorites" are not a smoking gun. Allow me to emphasize that the discussion I'll endeavor to have from this point forward will not be a rational extrapolation of the evidence at hand. Rather, I'm tugging at a loose, lunatic thread, gently pulling it across the room, seeing how it damages the weave, and ultimately trying to unravel something fundamental about the nature of life.
The question of the origin of life is at the root of considerable human endeavor: scientists work collaboratively over generations in the hope of parsing a concrete answer, theologians draft dogma, and artists celebrate the beautiful implausibility of the problem, honoring it each time they too make something from nothing. Why is panspermia -- the notion that life exists throughout the Universe, distributed by meteoroids, asteroids and planetoids -- any stranger than a touch from the Heavens, or a spontaneous spark in the primordial stew? The notion that life on Earth might have emerged, not from some local organic or mystical process, but from elsewhere, remains eccentric, marginal, and near-conspiratorial.
We may have difficulty conceiving of the Earth as anything other than the point of origin for consciousness, the shining beacon of life in a cold, dead universe. We see ourselves as Life, precariously existing on a pale blue dot that floats like a "mote of dust" in an infinite black vastness of Death. It's important to remember, however, that there's a difference between death and the absence of life. The universe is made of rocks, gas, and ample amounts of inert matter, but it isn't dead -- it's simply not alive. Life articulates its absence, which is to say, the universe appears to be dead, but only because it might kill us.
So, while we may imagine that meteors cutting through space*, burdened with genetic code, are arks of capital-L Life in a universe black with death, they are in reality life and death, birth, awareness, the seeds for conscious beings to spring forth and consider the question, the full spectrum of the conceit; the universe is just the substrate.
Perhaps panspermia also irks because life-from-elsewhere offends our human chauvinism. After all, the suggestion that we might exist thanks to an external catalyst reframes the narrative of human evolution, and of future human propagation out into the universe, from something like this:
To something more like this:
This changed narrative that the DNA meteorites imply -- a story in which humanity and all its grand pursuits is simply a waypoint in the journey of intelligence across the cosmos -- doesn't diminish the mystery of life. Rather, it widens the net, blooming the question outwards.
Life still had to emerge from non-life somewhere, sometime. To conceive of that occurrence on the home front is simply to displace the miracle; whether the spark occurred on Earth or not is immaterial. If anything, it's a bigger, better mystery -- one which is best appreciated if we think of if not as members of the human race, or even as denizens of the terrestrial biosphere, but as representatives of a vaster lineage: the living.
Evolution from Space: A Theory of Cosmic Creationism, by Sir Fred Hoyle and Chandra Wickramasinghe
The Biological Big Bang: Panspermia and the Origins of Life, collected essays including writings by Svante Arrhenius and Chandra Wickramasinghe
*Personal admission: I'm very nearly shattered by the idea of life as a variable of chaos upon an unfeeling backdrop of dust and gas.
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The current understanding, as I understand it, is that all the elements heavier than hydrogen come from stars and that everything past iron come from novas. Adding DNA, or nucleobase analogues, as it were, to the list of gifts from the wider universe doesn't seem out of place. It just makes us less likely to be unique and more a part of the universe.
In the most dispassionately rational way, panspermia or transpermia, the idea that molecules from which life could arise, are transported across space in small objects down to the size of dust particles, is hardly surprising and entirely reasonable.
The objection to that idea, at a level deep enough to have relegated it to the fringes for most of its history, is ultimately religious in nature: that God created the Earth as His special place, and God created all life on Earth.
The idea of special and unique creation persists even among many whose immediate reaction to creationism is to call for it to be a ticket to a psychiatric diagnosis. Special and unique creation has become attenuated via the secularism of science, into the paradoxical idea of "skepticism" of panspermia or transpermia to a degree that resembles nothing so much as an allergic reaction or some kind of psychodynamic defense.
Yet everything we know about physics and astrophysics tells us that there is no favored location. And the colloquial translation of that into a paradigm for everyday living, says that we are most likely only 1 out of a very large N, entirely unremarkable, not the least bit "special" or favored, and having unique value only as a particular variation on an otherwise common theme.
Yet that one small facet of unique value should be more than enough upon which to find a sense of meaning in relation to the greater whole.
Individual persons are each only 1 out of an N of size approaching seven billion. Individual persons have value only as particular variations on the otherwise common theme of an upright biped with a brain of such-and-such size and opposable thumbs.
Yet despite the fact that each human is only 1/7,000,000,000, we place a high value on each individual life, to the point where wanton or reckless destruction of lives violates the core moral codes of every culture known.
We say that each individual is "precious," is "priceless," is unique in a way that recognizes meaning and value in their life.
And so does it go for planets. On one hand we are microbes on a mudball in orbit around an unremarkable star, in all probability 1 over a very large N in this galaxy, an N of planets that are infested with life. On the other hand, our particular form of life, our particular culture, on this particular mudball with its unique ecosystems, is an individual case that is unlikely to have been duplicated in detail anywhere else.
Nowhere else in our galaxy, and probably nowhere else within our local universe, will there have ever been (or will there ever be) another Van Gogh, another Louis Armstrong, another Benjamin Franklin or Jaron Lanier or Claire Evans. Nowhere else will there be exactly the same life in all detail, as there is here.
Our value is our uniqueness as a variation on what is most likely a common theme. That value is not diminished one iota by the prevalence of life and even intelligent species and advanced civilizations elsewhere.
If anything, we should rejoice over the likelihood that we are indeed 1 over a very large N, and that our value is not in our being the only living world but a unique individual living world. We should rejoice that the universe is probably infested with life, and with intelligence. We should be supremely happy to be living in a universe that, weak anthropic principle fully admitted, is one that is more capable of giving rise to life and intelligence than almost any other universe we could conceive with any kind of consistent physical laws.
Some day, if we don't destroy Earth's climate and ecosystems, we can reasonably hope to put our best science into the form of the engineering needed to make multi-thousand-year journeys aboard Moon-sized colony ships, to the near stars, where we can reasonably expect to find microbes that evolved along similar lines to our own. Some day perhaps under an entirely different scientific paradigm we can barely imagine except in fiction, we may hope to make those journeys at a respectable fraction of c, and in our unguarded moments we may admit to hoping for the key to instantaneous travel across the span of the entire galaxy.
If there was no hope whatsoever of ever encountering evidence of another intelligent species, the urge to look up and above and beyond would be far less exciting. After all, who wants to move into a neighborhood with no neighbors whatsoever?
To make that kind of leap into space, or even the more modest one of posting enough space telescopes as to stand a chance of detecting some evidence of a distant civilization, we will have to overcome the deep-structure belief that a deity created us as "his" one-and-only. This is but one more reason to join the fight on that front, for comprehensive science education in the public schools, and for vastly improved scientific literacy in the general public.
I submitted a comment yesterday before comment 2 appeared, and almost certainly before 10:56 ScienceBlogs time. May I ask why it hasn't passed moderation?
This is not true, and my missing comment explains why.
Hi David, I am the sole moderator of this blog; sometimes it takes a moment for comments to post simply because I'm traveling or otherwise occupied. However, I can't find your comment from yesterday anywhere. It seems it didn't submit correctly. Try again? I'd certainly be interested to see this conversation develop.
Also, I love the notion of "ScienceBlogs time."
I don't think I have ever heard any objection per se to organic molecules from space -- after all the esteemed Carl Sagan devotes a whole chapter of Comet to the then-current understanding of the situation.
The objection to Wickramsinghe and Hoyle has more to do with the problem of getting to self-replicating molecules. If you posit that the actual life form -- something that replicates itself and metabolizes -- rained down to Earth that's fine, but then you still have the problem of where that came from.
In a nutshell: organic molecules Sure. CHON rains down all the damned time. Gas clouds have everything you could name in them -- formaldehyde, some aminos, probably -- the lot.
But there is as yet no evidence of full-on DNA there. And if life came from there in that fashion you would expect to see it.
Anyhow, the notion of building blocks of DNA doesn't seem so weird to me. But Wickramasinghe and Hoyle were going in a slightly different direction AIUI.
I mean, as g729 notes anything that is heavier than lithium comes from stars and supernovas. Life coming from elsewhere in an ultimate way is fine and dandy -- I know of no serious scientist who would disagree with that. It's when you get to origin questions closer to home that it gets trickier. And it is far from clear than anything but fragments of DNA would survive getting pulverized in a meteor strike.
The "genetic storms" idea seems doubtful to me at best. If that were the case you would expect to see loads more organic material and very complicated molecules falling in. Like orders of magnitude more. We don't see that. Horizontal gene transfer is all very well, and it happens, but saying that it would be source of genetic novelty from space when there are plenty of well-documented terrestrial sources seems shaky at best. I am not a geneticist, but IIRC you needn't propose a new molecule to get new genes -- you can rearrange the AGCT sequences to get that.
Thank you Claire for a very well researched and discussion provoking article here on Universe - and by saying so I also thank the fellow commentators above.
Ah, what a topic! From my own readings, ponderings, star-watching and mud-stomping, I would like to voice a synthesis of the already stated opinions: If a body in space were "receptive," that is, contained a mixture of suitable elements at certain surface temperatures, during a stage of atmospheric development, etc., and then were to be visited upon by extraplanetary material (let's go with Sagan and others here and say a comet - after all, water IS life and only half the water on our planet is accounted for by its own generation) than I think in theory we'd have the framework of our own planetary origins and those of other bodies in myriad galaxies.
I agree with your note, Claire - there might be a lot of gas and darkness out there, but with all the "chaotic" movements beyond, there exists great potential for variation, chance meetings, and the opportunities for some bodies with their own "miraculous" circumstances to produce beings such as ourselves, with an equally valuable and, so to speak, nutritious encounter. My main addition to this discussion though, is that a very commingling of generative materials seems to this mind, fundamental to the story of our collective origins - as it is to our individual selves.
Makes sense to me.
But then again, the idea that the existence is somehow predisposed to evolve, to constantly try and make itself in new ways, to improve itself has always been thrilling to me in a way that the Genesis story (at least as I was taught it as a kid) isn't.
To think that because of quantum fluctuations that "no-thing" is predisposed, naturally, to kickstart cycles of birth and decay is really very mystifying and wondrous.
I always had a feeling that the question 'and so who created God? And who created that which created God? And what created THAT?' and so on, was barking up the wrong tree.
It's not turtles all the way down.
It's fluctuations in the void, all the way up.
Religion never grabbed me the way that deep meditations on this mystery are able to.
Yah, I'm not a scientist...
@Yogi-one, I'm with you. I've never really seen a distinction -- in terms of initial supernatural awe -- between "God" and a vast unfeeling universe. Both inspire the exact same kind of questioning fear and perspective of personal inconsequence. My theory: the feeling of wonder that the universe instills in us all is the starting point from which (I imagine) spirituality, then religion, as well as science and the arts, evolved.
Nucleic-acid-peptide micro-molecular technology - a database of DNA through RNA intermediaries is implemented by the polypeptide interface. But this is an automated production system. A user who is? And this is an older subject - lipid membrane. Once upon a time, a few billion years ago, some engineers of a great civilization lipidoides created this nucleic acid-peptide technology and armed with it, settled by a million ships in all parts of the visible universe. But what do our evolutionists? And they are the origin and evolution of life on self-replicators - RNA! Wow! So you can keep your computer from the origin of a computer mouse! Yes, the computer system, of course at the last regular duplication mice formed a small detail, like user ...
I think the concept "extra-terrestrial" for life is not correct. Life is life. It is the same painful geo-anthropo-centrism. Intelligent life, armed with a nucleic-polypeptide technology could in a few billion years to spread widely in the universe, and here we have one of the planetary population. It is strange that you do not think this is correct!
Another interesting question. The above is obvious, but the crowd of smart people at NASA and elsewhere raise the question only about panspermia microorganisms! But why not a creative landing - a pan-noo-spermia? It's that - a taboo? I wonder who the customer? Ah yes, the theory of evolution as something is lost ... And creationism, too, seemed suddenly melts away! Because the origin of life in the universe moves away into the distance - for billions of years ago and in the world those creative lipidoids that have not yet created a DNA, proteins and many metabolic technologies ... And the theory of evolution is irreversible changes to the theory of de-evolution (and, strictly according to Darwin!) http://translate.google.com/translate?hl=ru&sl=ru&tl=en&u=http%3A%2F%2F…
To think that the first (maybe?) self organizing molecules might have come from somewhere else opens a vast (Carl Sagan's favorite word) set of possibilities. Taking off from Janna Levin's question (in "How the Universe got its Spots") "Is the universe infinite? or is it just really big?" led me to speculate on what might be out there beyond its boundary, so the idea of life on earth not necessarily being a closed system truly resonates with me. Thanks for the reminder.
The above is obvious, but the crowd of smart people at NASA and elsewhere raise the question only about panspermia microorganisms!
To d-r "Body Slim"
Sorry, Google has helped to translate incorrectly. I'll try anyway. Many in NASA speak of panspermia only microorganisms. But no pan-noo-sperm! Why? And because ...